Tuning of musical instruments is a difficult and tedious yet very necessary procedure for musicians. This is especially true when two or more instruments must be tuned to play at the same time. For example, musicians in an orchestra or a band must have their instruments in tune with each other, and tuned properly, before they can play music together. An even larger complication arises when the musicians or artists attempt to change to and from keys having different base interval relationships.
At times a group of musicians will start playing a song only to realize that one of the group needs to tune his or her instrument. Then a decision must be made to either continue playing out of tune or to stop, tune the instrument, and re-start. If this happens in front of an audience it can be very embarrassing. Of course, there is no guarantee that the state of tune will be any better following re-tuning. Furthermore, the time lost in re-tuning can be irritating to everyone.
Some musical instruments can be tuned in many different ways. For example, the guitar has a dozen different "open tunings", each of which has special advantages for playing certain songs. The performer usually does not want to retune during a performance so he brings to the stage a guitar for each open tuning he will use. Each such guitar must be separately tuned and must be maintained in that condition up to the time it is played. For several different open tunings, this procedure necessitates having several different guitars. This can be quite costly, and it also requires the performer to take the time to change guitars during a performance.
Furthermore, stringed instruments can change enough during a performance to go out of tune. This may be caused by a variety of factors such as humidity, temperature, and continued stress on the strings during playing.
Some musicians are better than others in tuning an instrument. As a result, some musicians are able to tune an instrument correctly in a reasonable period of time, while others (e.g. inexperienced musicians) may require a long period of time to tune and may not be entirely accurate in doing so.
Although there has been previously proposed a tuning apparatus (see, for example, U.S. Pat. No. 4,088,052) to detect the pitch in a stringed instrument electronically, such apparatus is not capable of automatically tuning the instrument. Furthermore, such apparatus can only tune one string at a time. There is also the possibility of error introduced by the mechanical portion of the system. Moreover, the apparatus uses analog filtering which has inherent limitations.
It is also necessary for the string being tuned to be vibrating during the entire tuning process. Another limitation of this apparatus is that it cannot compensate for the effects of neck warpage etc. during tuning of a guitar, for example.
Other types of tuning devices and tuning apparatus are disclosed in the following patents: U.S. Pat. Nos. 4,196,652 (Raskin); 4,207,791 (Murakami); 4,313,361 (Deutsch); 4,327,623 (Mochida); 4,426,907 (Scholz); and 4,584,923 (Minnick).
Each of the prior devices and apparatus exhibit various disadvantages and limitations, however. The primary disadvantage of the prior devices is that they utilize analog filtering of interfering signals to determine the frequencies generated by the instrument. This is not very precise. Furthermore, in an analog system the frequencies must be excited during the entire tuning process.
All of these prior devices are relatively slow in tuning. A device which tunes one string at a time must iterate several times to compensate for non-linear components. Also, none of such devices provide for friction in the nut or bridge. Locations of friction in a guitar or the like are the bridge and/or nut and the tuning peg mechanism. At the bridge or nut a string will move in short spurts due to differences between the coefficients of static and kinetic friction. That is, once a string begins to move it moves further than desired during tuning. The tuning peg mechanism involves considerable friction. Further, none of the prior devices provide compensation for non-linear effects. Non-linear effects include factors such as temperature changes and neck warpage. Nor do any of the prior devices have versatility which enables expansion for interfacing several instruments simultaneously.
For example, several of such devices are only capable of tuning one string at a time. Other devices have inadequate visual readout. Some of the devices are only capable of tuning to equal temperment, and some are only capable of tuning to predetermined frequencies with no variation possible. Also, the possibility of human error still exists with respect to the use of certain devices.
Certain of the devices are capable of tuning a string only when the string is vibrating with enough amplitude to fall into the constraints of the electronic components included in the device. If the amplitude of the signal is not great enough to enable the electronics involved, then the string cannot be tuned at all until the string is re-excited.
Further, certain of the devices use inadequate filtering techniques. Analog filters introduce phase errors into the filtered frequency. When the reference frequency is compared to the filtered frequency errors can occur because there is a phase difference in the two signals.
In yet another respect, some of the devices are mechanically complex and therefore are expensive and prone to unreliability if there is a mechanical failure.
One of the prior devices senses string tension as a means for changing the frequency. This technique has several inherent disadvantages. The number of vibrations per second is inversely proportional to the length of the string and the thickness of the string. It is also proportional to the square root of the tension to which the string is subjected. Finally, the number of vibrations is inversely proportional to the square root of the density of the string. The thickness or cross-sectional area of the string changes in character chiefly due to the stress on the string during playing. Because of the changes in the cross-sectional area the frequency is not in a perfectly linear relation to the tension. Consequently, this method of sensing tension is inferior.
None of the prior tuning devices or apparatus provide the advantages exhibited by the system and techniques of the present invention.